The invention relates to suppressing recombination in an electronic device.
Various types of electronic devices include semiconductor material structures that convert energy between photons and excited bound electron-hole pairs called “excitons”. Light absorbing devices such as photodetectors and solar cells (e.g., “photovoltaic cells”) generate excitons from absorbed photons. The separation of the electron and hole of an exciton to separate cathode and anode electrodes, respectively, contributes to a generated electrical current. Recombination of free electrons and holes reduces the electrical current and the resulting efficiency of the device. Light emitting devices such as light emitting diodes (LEDs) generate photons from injected electrons and holes while solar cells generate electrons and holes from incident photons. Various types of semiconductor material structures can be formed. For example, photodiodes can include p-n junctions or p-i-n structures. A phototransistor can generate photons from a transistor structure. An LED can also be formed from a p-n or p-i-n structure, and emits light when forward biased.
Different devices include different types of materials. Some devices such as organic solar cells and organic electroluminescent devices (or organic light emitting devices “OLEDs”) incorporate organic materials. Some devices include a thin layer of a material on an electrode of a structure to enhance their performance. For example, an electron injection layer (or “electron-transport layer”) on an electrode can be used to improve the performance of OLEDs. Some devices use an exciton blocking layer on an electrode to prevent excitons from arriving the electrode and thereby increase the efficiency of the device, such as a solar cell. Some organic devices use an inorganic “buffer layer” between the anode and an organic hole-transporting layer to enhance the electroluminescence of the organic device.